This invention relates generally to a method of processing a gas mixture. More particularly, it relates to a process for recovering ethane and heavier hydrocarbon components from a methane-rich gas.
Methane-rich gases, for example natural gas, usually contain small but significant amounts of higher boiling heavier hydrocarbons such as ethane, propane, butane and the like. These components are quite valuable as feed stock for the manufacture of various petrochemicals and for the production of liquefied petroleum gas. It is therefore desirable to separate these various components prior to sending the lighter gases, i.e., the lean gases that will remain, to the fuel distribution system.
In the conventional process for separating components of natural gas, said components having varying boiling points, the so-called methane cycle is employed. In the conventional low temperature process for the separation of a gas mixture, the gas mixture to be separated is introduced, preferably in the liquid phase, into a rectification tower at about the midpoint thereof, the heavier components being concentrated in the stripping section below the feed point in the column. The vapor mixture within the column at the feed point rises in the upper enrichment section of the column and is enriched in the lower boiling point component. The gases collecting at the top of the column are then in part passed through a high pressure cycle wherein they are compressed, cooled, and liquefied, expanded, and re-introduced into the rectification column as reflux liquid.